Phytosterols for hair: what are the effects?

The application of a treatment containing phytosterols can reduce scalp irritations and feelings of discomfort. These plant compounds indeed have anti-inflammatory and soothing properties. They are capable of inhibiting the activity of enzymes that play a significant role in the synthesis of prostaglandins, namely lipoxygenase (LOX) and cyclooxygenase (COX). It's worth noting that prostaglandins are molecules responsible for several inflammatory phenomena such as itching or pain.

Furthermore, phytosterols have an impact on the activation of pro-inflammatory transcription factors, notably the nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1). These transcription factors play a crucial role in the regulation of gene expression coding for pro-inflammatory proteins. Phytosterols interfere with these signalling pathways, leading to a reduction in the production of pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumour necrosis factor (TNF-α). Thus, phytosterols soothe and relieve the scalp by reducing sensations of discomfort.

To prevent split ends and breakage, it is crucial to provide daily adequate hydration to your hair. Phytosterols can contribute to hair hydration due to their moisturising properties. Indeed, they have the ability to capture and retain water, and help to limit its evaporation.

Note : It is wise to remain cautious about the moisturising properties of phytosterols on hair. Indeed, these properties were first identified in skin and, so far, they have been very minimally studied in the haircare field.

The application of a treatment based on phytosterols to hair fibres could slow down the greying of hair due to the properties antioxidants of these compounds. Studies have indeed highlighted a link between oxidative stress and greying hair. Free radicals generated by UV rays, pollution or even tobacco degrade melanin, the pigment that gives hair its colour, via a series of reactions. It is also worth noting that free radicals are likely to weaken the hair bulb and promote hair loss and split ends.

Phytosterols protect hair from free radicals due to their chemical structure. This structure is rich in double bonds, which allows them to neutralise these reactive species through a donation of an electron. Furthermore, some studies suggest that phytosterols can stimulate the activity of endogenous antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase. These are essential proteins in the mechanism of eliminating free radicals.

It has recently been highlighted by a study conducted in vitro that β-sitosterol, a phytosterol found in the seeds of certain plants, could inhibit the growth of golden staphylococci, Gram-positive bacteria. However, the mechanism of action of β-sitosterol has not been determined. Even though further tests targeting other bacteria would be necessary, this study suggests that phytosterols could be useful in combating certain bacterial infections affecting the scalp.

• CABRAL J. & al. Phytosterols: applications and recovery methods. Bioresource technology (2007).

• SEIBERG M. Age-induced hair greying - the multiple effects of oxidative stress. International journal of cosmetic science (2013).

• SURINA I. & al. Antibacterial and antifungal activity of phytosterols and methyl dehydroabietate of Norway spruce bark extracts. Journal of biotechnology (2018).